1. Field of the Invention
The present invention relates to a light for an aircraft with a housing, comprising a light source and a reflector forming a bundle of light of the light emitted by the light source for generating a predetermined light distribution, and with a translucent cover for closing the housing.
2. Description of the Background Art
It is common to equip lights with incandescent lamps and a reflector to generate, as a position light, for example, a desired luminous intensity distribution (e.g., German Patent 41 17 289). In aircraft, it is known that for lights arranged on exposed positions of the aircraft, e.g., at the free ends of the wing or in a rear portion of the craft, different luminous intensity distributions in vertical and horizontal directions are predetermined. From the advertising documents of the company Hella KG Hueck and Co. xe2x80x9cHELLA Aircraft Equipmentxe2x80x9d, a light (No. 2LA 001 625-xx) is known which satisfies a predetermined horizontal luminous intensity distribution in a range between +/xe2x88x9270xc2x0. The light comprises a housing wherein as a light source, an incandescent lamp is arranged coaxially with the housing. The incandescent lamp is arranged in a rotationally symmetrically configured reflector reflecting the light emitted by the incandescent lamp according to the predetermined light distribution. A front edge of the housing serves as a boundary edge for the emitted light bundle. A disadvantage of the known light is that the luminous intensity of the incandescent lamp has to be designed for being relatively high to satisfy the requirements as to the predetermined luminous intensity distribution. As a consequence, the minimum luminous intensity in some parts of the predetermined solid angle range of light radiation has to be exceeded by far so that the luminous intensity in other parts of the solid angle range of light radiation is barely above the minimum luminous intensity valid for these parts.
It is therefore an object of the present invention to provide a light for an aircraft in such a manner that it is ensured to achieve a predetermined luminous intensity distribution with an increased efficiency.
To solve this object, the present invention provides a light, particularly a position light, for an aircraft, preferably for being mounted to the rear end of an aircraft, such as, e.g., an airplane, which is provided with a luminous device for emitting light, a reflector arrangement, and a housing comprising a receiving room for the luminous device and the reflector arrangement covered by a transparent cover, which are configured such that light, with a minimum intensity required along a preferential axis, emerges from the housing.
According to the invention, this light is characterized in that the luminous device includes a first and a second light source which are substantially identical and respectively emit light within a light radiation solid angle with a central axis, the two light sources are arranged symmetrically to the preferential axis and the central axes of the light radiation solid angle is inclined so as to face each other. The reflector arrangement includes a first and a second reflection surface allocated to the first and second light source, respectively, the reflection surfaces also being symmetrically arranged to the preferential axis and respectively provided with a light propagation limiting edge for limiting the light propagation range, within which light emitted directly by the respectively allocated light source emerges from the receiving room of the housing. The first reflection surface is arranged opposite to the first light source and the second reflection surface is arranged opposite to the second light source. The light propagation limiting edge of the first reflection surface faces away from the second light source and the light propagation limiting edge of the second reflection surface faces away from the first light source. The two reflection surfaces are oriented and/or configured such that light emitted by the one light source is reflected by the reflection surface allocated thereto past the light propagation limiting edge of the other reflection surface to increase the luminous intensity within the light propagation range of the other light source near the partial range defined by the light propagation limiting edge of the one reflection surface.
In the light according to the invention, the use of appropriately arranged reflection surfaces (as is indicated above) achieves that the requirements, particularly with respect to the light/dark border of light distribution functions, can be satisfied while using as few light sources as possible. This is particularly possible when LED elements or LED modules are used as light sources. The advantage of LED elements compared with conventional incandescent lamps (with spiral-wound filament or configured as flashtube) is that LED elements have a substantially longer service life. Moreover, LED elements are substantially less sensitive to interferences. Moreover, LED elements can be operated in a substantially smaller and lower voltage range than conventional incandescent lamps. Finally, the power consumption of LED elements is substantially lower than that of incandescent lamps. All this leads to advantages in technical and particularly also in economical regard, therefore, the aircraft industry and aviation companies are increasingly interested in the use of LED technique in the exterior lighting area of aircraft.
It has to be pointed out in this context, however, that the invention is not limited to LED elements as light sources but that conventional incandescent lamps can also be used as light sources or luminous device.
A certain disadvantage of LED elements is only their limited radiation angle range of from 120xc2x0 to 180xc2x0 (depending on the type). Therefore, it is required that the legal or international requirements in aviation as to the horizontal and vertical luminous intensity distributions of position lights on airplanes are satisfied in spite of this relatively limited solid angle radiation range by appropriately arranged reflection surfaces.
In a further embodiment of the invention, the reflector arrangement includes a third and a fourth reflection surface which are allocated to the first and second light source, respectively, and are also arranged symmetrically to the preferential axis and between the first and the second reflection surface when seen in a top view of the cover in the direction of the preferential axis and reflect the light emitted by the respectively allocated light source substantially in the direction of the preferential axis.
Suitably, the reflector arrangement has a fifth and a sixth reflection surface also arranged symmetrically to the preferential axis and offset by 90xc2x0 with respect to the first and the second reflection surface, the fifth and the sixth reflection surface reflecting the light emitted by both light sources within a first solid angle range adjacent to the preferential axis. Suitably, the fifth and sixth reflection surfaces interconnect the first and second reflection surfaces.
In further embodiment of the invention, it is further provided that the reflector arrangement includes four seventh reflection surfaces which are diametrically opposed to each other in pairs and are arranged symmetrically to the preferential axis in pairs, that two seventh reflection surfaces are allocated to one light source, respectively, and that the four seventh reflection surfaces reflect light of the light sources respectively allocated thereto within a second solid angle range spaced from the preferential axis. Particularly, the first solid angle range is located between the preferential axis and the second solid angle range.
Particularly, the third and fourth reflection surfaces as well as the four seventh reflection surfaces are configured as parts of the surface of a common first reflector body, which, in top view of the cover of the housing, viewed in the direction of the preferential axis, is arranged between the two light sources. It is also advantageous if the first, the second, the fifth and the sixth reflection surface are configured as a second annular reflector body, which, in top view of the cover of the housing, viewed in the direction of the preferential axis, is arranged in front of the two light sources.
In a further embodiment of the invention, in a top view of the cover of the housing, viewed in the direction of the preferential axis, the light sources are arranged behind the second reflector body and in front of the first reflector body.
Preferably, the reflection surfaces have a curved, particularly concavely curved configuration.
In a further embodiment of the invention, each of the two light sources is configured as a light source comprising at least one LED element, each light source being particularly configured as an LED module with a plurality of LED elements arranged in the form of a matrix or a lattice.
Further, for the illumination in directions of 90xc2x0 to the preferential axis, it is suitable to provide further light sources arranged in such a manner that they emit their light under an angle of substantially 90xc2x0 to the preferential axis, these further light sources include at least one LED element each.
For the identification friend-foe it is suitable when additional radiation sources emitting electromagnetic radiation in the non-visible wavelength range are provided and arranged in such a manner that they emit their radiation substantially in the direction of the preferential axis, these radiation sources being adapted to be driven to supply the radiation pulsatingly, intermittently and/or continuously. Preferably, these additional radiation sources are configured as LED element, particularly as IR-LED element.
To solve the above object, a light is provided according to a modification of the invention which is provided with a housing containing a luminous device and a reflector arrangement forming a bundle of light of the light emitted by the luminous device for generating a predetermined light distribution within a predetermined solid angle range with a preferential axis, and a transparent cover locking the housing.
This light has a reflector arrangement that includes several reflection surfaces which are differently oriented and arranged next to the luminous device so as to be transversely offset with respect to the preferential axis, the luminous device being positioned obliquely relative to the preferential axis.
The particular advantage of the light according to the invention is that by the configuration of differently oriented reflection surfaces, the light emitted by the light source can be specifically led to the generation of a predetermined luminous intensity distribution. Thus, the standardized photometric requirements can be satisfied with relatively small efforts. The basic thought of the invention is to achieve a desired minimum luminous intensity distribution in a predetermined solid angle range by differently oriented reflector surfaces under energetically optimized conditions and particularly by the use of LEDs or LED modules. Due to the fact that reflection surfaces are positioned in an arrangement transversely offset with respect to the main radiation direction (preferential axis) of the light, a large solid angle range can be covered by the light beams emitted by the light source arranged obliquely to the main radiation direction. Thus, the light beam can be deflected in a large angular range without the reflection surfaces having an undesired shading effect.
According to a particular embodiment, the reflector has a first (inner) and a second (outer) reflector body or segment, each of which has a number of differently oriented reflection surfaces. The outer reflector segment includes at least two reflection surfaces to generate a broad light distribution section with relatively high light intensity. The inner reflector segment includes small reflection surfaces, which may be configured independently of the orientation of the reflection surfaces of the outer reflector segment. The inner and outer reflector segments can either be integrally connected to each other or they can be configured as separate components. It is essential that the structural shapes of the reflection surfaces of the inner reflector segment on the one hand and the outer reflector segment on the other hand can be configured independently of each other. The only condition is that the reflection surfaces of the inner reflector segment do not project so far as to shade the reflector segments of the outer reflector segment arranged on that side of the inner reflector segment facing away from the light source.
As an alternative, the reflector segments can be arranged terrace-shaped at a different distance from the light source The reflector segments that are further away from the light source being constructed so as to be higher in the main radiation direction of the light.
According to a further aspect of the invention, the light includes light sources that are arranged obliquely under an acute angle to the main radiation direction thereof, the reflection surfaces of the outer reflector segment functioning so as to reflect the light beams emitted by the first and the second light sources, respectively. The reflection surfaces of the inner reflector segment each serve only to reflect the light beams either of the first light source or of the second light source.
According to a further aspect of the invention, the light sources as well as the reflection surfaces of the outer and the inner reflector segments are arranged symmetrically to a central plane of the light. Thus, a particular simple structure of the light is possible. As an alternative, it is also possible to arrange more than two light sources, e.g., under an angle of 120xc2x0 or 90xc2x0, in a circumferential direction to the main radiation direction.
By providing several light sources, a redundancy can be created which prevents an absolute operative failure of the light.
According to a preferred embodiment, the light sources are configured as LED modules (light-emitting diode modules), each of which has a plurality of light-emitting diodes arranged in the form of a lattice on a carrier plate. By the use of light-emitting diodes, the power consumption can be decreased and the life expectancy can be substantially increased, respectively. By a failure of the light-emitting diodes, a spectrum can be realized in particular which spares a wavelength range interfering with the operation of a night viewer. It is not necessary to provide a filter glass and thus, an additional night view filter is not required.
According to a further aspect of the invention, the inner reflector segment comprises at least one opening for the passage of light beams of a further radiation source, preferably a radiation in the invisible wavelength range, e.g., of an infrared light source. Through appropriate drive, the infrared light source is suitable for transmitting optical identification signal patterns for the identification friend-foe for military purposes.
In connection with the two modifications described above and the developments thereof, reference was made to a plurality of features and feature combinations. It has to be noted that features described in connection with the one modification of the invention may also be used with another modification. In this respect, the invention covers all combinations of the features described before.